Facile synthesis of silica aerogel supported K2CO3 sorbents with enhanced CO2 capture capacity for ultra-dilute flue gas treatment

Silica aerogel supported K 2 CO 3 sorbents with different K 2 CO 3 loadings were synthesized by sol-gel and wet impregnation processes. The sorbents were characterized by N 2 adsorption-desorption, X-ray diffraction (XRD), and field emission scanning electron microscopy (FESEM) techniques. CO 2 capture performances of the sorbents were tested in a simulated ultra-dilute flue gas stream of 1.0%CO 2 and 2.0%H 2 O at 20 °C, using a fixed-bed reactor coupled with an online infrared gas analyzer. Sorbent regeneration performances of the samples were evaluated in a pure N 2 atmosphere at 200 °C with a heating rate of 10 °C/min. CO 2 capture capacity and K 2 CO 3 utilization efficiency increased first and then decreased with the increase in K 2 CO 3 loading. The desired sorbent with 20 wt% K 2 CO 3 was screened for investigating the effects of acid impurities. The presence of 500 ppm SO 2 and 500 ppm NO in the simulated flue gas stream was found to adversely affect the CO 2 capture, sorbent regeneration and multiple cyclic performances. Detailed mechanisms of the irreversible sorbent deactivation process were discussed. SO 2 could be chemically absorbed by K 2 CO 3 under a moist condition to form byproduct of K 2 SO 3 ·H 2 O, and the byproduct was stable and would be accumulated in the sorbent during the repeated cycles. This further attenuated the physical properties and K 2 CO 3 utilization efficiency of the sorbent. These results would lay a solid foundation for further application of the sorbent in ultra-dilute flue gas treatment.